The present invention is directed to a control system for use with an internal combustion engine connected to a load through a variable speed transmission. In the utilization of an internal combustion engine and in particular a diesel engine in off-the-road equipment, it is found that ordinarily the operators of these engines operate the engine at the maximum horsepower of the engine. It has been found that in many instances it is desirable to reduce the horsepower when the engine is connected to a low speed ratio through a transmission to conserve fuel and to protect the power train. In addition, it is also desirable to reduce the engine horsepower when the engine starts to overheat. The reduction of the horsepower, when an engine starts to overheat, is dependent upon the care which a given operator utilizes in watching the condition of the engine. In certain instances, an operator pays little attention to the temperature of the engine and will continue to operate the engine at maximum horespower even though the engine is overheating. The continued use of an overheated engine results in damage to the engine.
The prior art discloses the utilization of devices for controlling the rate of delivery of fuel to an engine. A typical prior art device is disclosed in U.S. Pat. No. 3,107,483, issued Oct. 22, 1963 to W. L. Hamilton and entitled "Fuel Control for Engines". Another system for limiting the torque of an engine is taught in U.S. Pat. No. 3,914,149 to Sale et al, issued Oct. 21, 1975 and entitled "Torque Limiting System and Method".
Although the prior art recognizes the desirability of limiting the torque in certain instances, the prior art does not teach a system which utilizes a horsepower limitation of an internal combustion engine, when the engine is overheated or when the equipment is operating at a low speed gear ratio. It is a principle object of this invention to provide a simple and economical system which automatically protects an internal combustion engine when the engine is overheating or when a transmission connected to the engine is in a low gear.